1. Field of the Invention
The present invention relates to an energy storage system. More particularly, the present invention relates to a compact energy storage system which is capable of storing a plurality of energy storing devices.
2. Description of the Prior Art
It has long been thought that electric batteries might serve as the main component in energy or utility storage systems. However, most batteries either do not have adequate electric energy storage capacity to meet the demands of energy storage systems, or are very costly and, therefore, are inappropriate for such applications.
Energy storage applications involve the use of an energy storage system in order to supply electric power to an electric power transmission system during times of peak usage. It is well known that the demand for electric power fluctuates. Normally such fluctuations occur on a relatively regular basis. For example, in a typical residential electric power grid, demand for electric power is low at night, peaks during the morning, levels during the day, and peaks again in the late afternoon and into the evening.
Electric power utility companies use a variety of techniques to meet fluctuating demand while maintaining a relatively constant level of electric power production. For example, electric power utilities may use electric power to pump water into reservoirs during off-peak times, and then release the water from the reservoirs to hydro-electric generators during peak times to produce electrical power. However, there are circumstances where the demand for electric power suddenly and irregularly increases. One such instance is where cold weather strikes cities and communities that normally experience moderate temperature conditions. From the perspective of an electric power utility company, the associated increase in electric power demand occasioned by such weather occurrences is difficult to handle because the weather conditions and the increase in electric power demand are short lived. One way to handle short lived, irregularly occurring electric power demand increases is to electrically couple an electric energy storage system to an electric power transmission system so that the energy storage system may be utilized, or turned on, to provide additional electric power during peak demand. In particular, such a system would be useful if it was portable so that it could be placed at various locations in an electric power grid rather than at a generating source, such as a steam generator power plant. Such a storage system could feed electric power to that portion of the electric power grid experiencing a sudden, short lived increase in electric power demand such as might be occasioned by a period of cold weather. Thus, the storage system would supplement the power transmission system and prevent increased electrical power demand experienced by one portion of the electric power transmission grid from affecting other portions of the grid.
Although the benefits of a utility storage system have long been recognized, as noted above, prior-art batteries, and battery systems, have proven incapable of providing the high power output required for use in utility energy storage applications at a reasonable cost. Presently, batteries used in large storage systems are designed for use as auxiliary or standby power sources. Large battery installations are employed to provide electric power in emergency or power-failure circumstances, not to provide supplemental power to an electric power grid during demand peaks. Typically, large lead-acid batteries are used as standby power sources. For example, lead-acid battery systems providing 2000 ampere hours (Ah) are typically used to provide emergency lighting. Lead-acid battery systems providing 15,000 Ah are commonly used as standby power sources for telephone exchanges. Such battery systems, though relatively long lived, are extremely expensive and relatively large in size. In addition, such battery systems do not have the necessary electrical storage capacity per unit area to meet the demands of all electric energy storage applications.
Storage capacity per unit area is a significant factor for utility energy storage applications. High density storage batteries and energy systems are of higher value to electric utilities because they are, in general, more readily transported. The capacity of a battery is usually expressed in ampere hours, which is the product of current in amperes multiplied by the current flowing in the time of one hour. Battery capacity may also be expressed in terms of watt or kilowatt hours (kWh) which is the product of the power, or ampere-volts, multiplied by the time power is provided. However, a more informative measure of battery capacity is that of Ah or kWh per unit area. Presently, electric power utilities are seeking energy storage systems having storage capacities in excess of 100 kWh and as high as 5 to 10 MWh to supply supplemental power to a portion of an electric grid. However, at the same time, electric utilities require that such systems fit within an area of less than about 400 square feet and that such systems be relatively inexpensive.
Until recently such utility energy storage system have been impossible to achieve. However recent advances in battery technology have made it possible to produce batteries with a relatively high storage capacity per unit area at a relatively low cost.
In particular, advances in zinc-bromine battery technology have made it possible to create an energy storage system which has a high energy storage capacity and which is relatively lightweight and portable. In addition, zinc-bromine battery energy storage systems have significant cost advantages over other battery technologies. Of course, regardless of the battery or electric energy storing device technology used, an energy storage system must achieve maximize energy storage capacity in minimal space. Also, such systems must be easy to maintain. In addition, any portable system must be capable of sheltering the energy storing devices stored within it, while simultaneously preventing materials from the energy storing devices from contaminating the environment outside the storage system.
What is needed, therefore, is an energy storage system that has an energy storage capacity of greater than 100 kWh. Further, what is needed is a energy storage system that is relatively inexpensive, lightweight, and compact compared to previously known systems. Further what is needed is an energy storage system that is portable. Further, what is needed is an energy storage system that provides easy access to the batteries being used therein for purposes of replacement and maintenance. Further, what is needed is an energy storage system that provides shelter for energy storage devices. Further, what is needed is an energy storage system that is capable of containing materials within the system which if leaked or otherwise disbursed would cause damage to the environment outside the energy storage system. Lastly, what is needed is an energy storage system that may employ various electric energy storing devices including batteries.